Underwater mine

“ Some of the new features were the development of depth-charge throwers, the manufacture and use of fast coastal motor-boats for anti-submarine work, the production of mines of an improved type for use especially against submarines, very considerable developments in the use of minefields, especially deep minefields, including persistent mining in the Heligoland Bight and the laying of a complete minefield at varying depths in the Straits of Dover; also, after the United States entered the war, the laying of a very extensive minefield right across the northern part of the North Sea. ”

“ Mines for the open sea in great numbers, moored “flying”—that is, by ships steaming at considerable speed—need anchors with automatic depth regulation. Such mechanism had undergone important changes during the war, and the new American mines needed all the improvements, to make them sure to plant at the intended level. ”

“ In a few of the largest collieries it has been found advantageous to establish underground stationary engines, which bring the trains of waggons, by means of an endless rope, along the galleries to the bottom of the shaft. In other mines, such as those of Worsley in Lancashire, subterranean canals are cut, upon which the mineral is transported in boats.
In the European mines, the ores are usually lifted from the bottom of the shaft to the surface by steam-power, or horse-gins; but in Spanish America, men, and even women, are employed for this purpose. ”

“ Upon the bed-rock is a deposit, from three to four feet in depth, of gravel and boulders, in which the gold is hidden. This is called by the miners "pay-dirt," and to remove it to the surface and wash it is the end of mining. It is an expensive and laborious process indeed. The water has first to be controlled; and in mines of not too great depth this is done by a drain ditch along the bed-rock, commenced many claims below. In this all the claim-holders are interested, and all contribute their quota of the labor and expense of digging it. ”

“ The shafts are wide, the galleries high enough to allow one to walk upright through them. The upper stories are almost thoroughly dry, the lower ones humid; the water, however, is easily removed by hand-pumps, which raise it from story to story into a large subterranean reservoir, emptied once a week by a steam-engine of fifty-four horse-power. The veins are so extremely rich that, though they have been worked pretty constantly during so many centuries, the mines have hardly reached the depth of 1,140 feet. ”

“ A submarine mine of to-day consists of a mine case, shaped like a ball or egg, about one yard in diameter, mounted on an anchor in the form of an iron box about 30 inches square, connected by a wire rope mooring cable, about 3⁄8 inch in diameter. The mine case contains the charge of high explosive—300 pounds of TNT in our mines—and the firing mechanism. The combination stands about 5 feet high and weighs 1400 pounds. Four small car wheels on the anchor run on steel tracks, allowing the mines to be easily moved along the decks to the launching point. ”

“ Where appreciable current exists, a heavy sea may cause mines to step along, or “migrate”—there is no telling how far—and the danger from mines adrift is naturally greater near a minefield than elsewhere. Mines are designed to become safe on breaking adrift and many of them are, but far from all. Submergence in salt water may derange the mechanism for that safety purpose. There was very little current across Area A, however, and the fine tactical qualities shown by the squadron lent confidence that it could be safely conducted much nearer to our minefields than five miles. ”

“ For the purpose of better ventilating the mine, an enormous fan, forty feet in diameter, formed like the paddle-wheels of a steam-ship, and kept constantly revolving by steam-power, was placed over a shaft sunk for that sole object. The suction caused by the enormous paddles drew up all the foul air and noxious vapours from the whole of the mine, and at the same time drew in from another shaft, more than a mile distant, a current of fresh air, amounting from 70,000 to 80,000 feet per minute, thus doing the work of a furnace far more effectually, and at much less cost. ”

“ Before leaving the question of shale mining, it should be explained that the shale miner is subject to dangers much as his colleague in the coal-pit, but the volume of gases found in the shale seams is not so great as in the coal measures. These, however, are 140 of an explosive nature, the most common being fire-damp.
Once above ground, the shale is conveyed to breaking machines by endless wire-rope haulage. Passing through the machines, it is broken into suitable sizes for distillation, and drops into hopper-shaped hutches. ”

“ Imagine the descent into a mine through the sea, the miners working at the depth of 12 fathoms below the waves; the rod of a steam engine extending from the shore to the shaft, a distance of nearly 120 fathoms; and a great number of men momentarily menaced with an inundation of the sea, which continually drains in no small quantity through the roof of the mine, and roars loud enough to be distinctly heard in it.” Tin is the principal produce of this mine, and the ore is extremely rich. ”

“ Indeed, when we consider the measure of the underground cavities which miners have excavated, we cannot but be surprised that grave catastrophes have not often resulted from the removal of the foundations on which the crust of our earth is laid. The 100,000,000 tons of coal yearly extracted from British mines require the withdrawal of subterranean strata equal to an area of 20,000 acres one yard deep, or 2,000 acres ten yards deep. These excavations have gone on for several years at this rate, and in smaller proportions for centuries. ”

“ An account is given of the mine barrage in the North Sea, one of the outstanding anti-submarine offensive projects of the year, thus closing the North Sea, and for which 100,000 mines were manufactured and 85,000 shipped abroad. A special mine-loading plant, with a capacity of more than 1,000 mines a day, was established by the Navy Department.
A star shell was developed which, when fired in the vicinity of an enemy fleet, would light it up, make ships visible, and render them easy targets without disclosing the position of our own ships at night. ”

“ A gold mine now consists of a shaft or pit dug several hundred feet down into the rock, with levels or galleries running off from it and with big openings like rooms made where the rock was dug out. The roofs of the rooms are supported by great timbers. To break away the rock, the miner makes a hole with a rock drill worked by electricity or compressed air, puts powder or dynamite into the hole and explodes it. The broken rock is then raised to the surface and crushed in a "stamping mill." Here the ore is fed into a great steel box called a "mortar." ”

“ Although the metal miner is subjected to fewer accidents than are his brethren working in coal mines, the atmosphere in the former is far more destructive to human life. In lead mines, the duration of life averages scarcely more than thirty-two years, and in those containing arsenical pyrites or quicksilver ores, the average is still lower. Before the use of gunpowder in underground operations, the rocks containing the ore were attacked with fire, indeed the practice is still retained in some countries. ”

“ The mine is like a large quarry, with a number of small excavations which fill with water, and are pumped by most ingenious Chinese pumps worked by an endless chain, but there are two powerful steam pumps at work also. About four hundred lean, leathery-looking men were working, swarming up out of the holes like ants in double columns, each man carrying a small bamboo tray holding about three pounds of stanniferous earth, which is deposited in a sluice, and a great rush of water washes away the sand, leaving the tin behind, looking much like "giant" blasting powder. ”

“ Perhaps there was seldom seen a grander fight between love and death.
Those who had a thorough knowledge of the mine, soon perceived that thirty-eight yards of solid coal intervened between the imprisoned men and their rescuers. The only other access was completely cut away by so vast a body of water, that it was not unfitly compared to an underground ocean. The obstacles between the rescuers and the imprisoned men seemed at first insurmountable. It appeared to be beyond human strength, either to drain away the water, or to cut through the coal, in time. ”

“ Mining accidents come in a few cases from failure to provide the best appliances in the mines, but in many cases are due to carelessness or ignorance of the operators themselves. There still remain a large number of accidents which occur in the best regulated mines, and when no instance of special carelessness can be traced. For years these disasters have puzzled mining engineers, but within the last few months it has been discovered that the minute particles of coal dust in a dry mine completely fill the air, so that the air itself is ready to burn. ”

“ When a mine is so situated that drainage galleries cannot be established, engines must be employed for pumping up the waters. Thus, in Cornwall, where most of the copper mines open almost at the sea level, an enormous influx of water can be kept in check only by an equally enormous steam-power. In the United and Consolidated Mines between Truro and Redruth, seven steam-pumps, working with the united strength 272of 2,000 horses, are kept constantly in motion, and raise above 2,500,000 gallons of water in twenty-four hours. ”

“ The drowning of a coal mine not seldom occurs from the irruption of water accumulated in old wastes or ancient workings occupying a higher level in the vicinity. The growing pressure of such a body of water upon the beds or barriers below becomes enormous; and then the water, testing every weak point of the body opposed to its escape, at length unexpectedly rushes into the space which it finds open before it. All the works below are completely filled, and the mines are for a time rendered useless, or, it may be, for ever abandoned. ”

“ FIG. 100.—HYDRAULIC MINING ON THE KLAMATH RIVER, CALIFORNIA As the rocks upon the surface decay and the crumbling material is carried away by running water, the gold, being very heavy, washes down the hillsides and is at last gathered in the gulches. This fact explains why we find gold both in veins and in the gravel of the streams. Getting gold from the veins is called quartz-mining. Washing it from the gravel is called placer-mining; and if the gravel is deep and a powerful stream of water is required, the work is called hydraulic mining. ”

“ They could, granted science and intelligence enough, construct great mines in vast numbers. These, if attached to air-filled globes, would be swept instantly up to the ocean's surface when released. They would float there indefinitely, and any ships cruising to and fro would sooner or later strike one and be destroyed, unless they were warned by the previous destruction of one. In this way the creatures of the sea's depths could prevent our cruising above and trawling for them. ”

“ Since 1898, however, deep and yet deeper depths have been explored, especially in following the richer reefs, and always with the similar result of meeting with the same, or a superior, grade of ore contents peculiar to the higher sections of the particular reef, so that the inference is strengthened to certainty that profitable exploitation is only limited to the ultimate depth at which modern mining can be carried on. The problem, therefore, is one for the engineers ”

“ In the ground mine, the case contains the explosive and the firing device, and is heavier than the displaced water; it therefore rests upon the bottom and requires no anchor. Ground mines are not used where the depth of water exceeds 35 feet. ”

“ Another important problem that constantly confronts the mining engineer is that of drainage. Mines are, of course, great reservoirs for the accumulation of water, which must be drained or pumped out continually; and as the shafts are sunk deeper and deeper it becomes increasingly difficult to raise the water to the surface. ”

“ There is only a hole in the ground, where mining is carried on in much the same manner as in other kinds of mines. The shaft is sunk and lined with timbers to keep the dirt from falling in, just as in other mines. In working salt mines, however, water is almost as bad as earth, and therefore a layer of clay is put between the timbers and the earth. There are the usual galleries and pillars, with roof and floor of salt. The workmen try to get the salt out in lumps or blocks as far as possible, and so they bore in drill holes and then blast with dynamite or powder. ”

“ As the coal is mined a certain proportion of it is ground into powder, and this fills the air and becomes a powerful explosive. Precautions are taken in most cases. The mines are sprinkled and state and national governments have done much to make mining safe, but at the best the occupation claims an unusually heavy toll in life and limb. ”

“ Besides the danger of being crushed to death by a fall of rock, or immured in a living tomb by an obstruction of the shaft or an irruption of water, the miner has another, and often still more formidable, enemy to encounter in the noxious gases frequently evolved in coal-pits. Thus in all well-regulated mines the greatest attention is paid to ventilation, so that no part of the workings may be left without a proper supply of air. In ordinary cases the natural currents, which set in different directions through the shafts and galleries, may sufficiently purify the atmosphere ”